Case Report: Treatment trade-off - The Horse Owner's Resource

Case Report: Treatment trade-off

Surgery to remove the rare tumor behind my horse’s eye carried the risk of serious complications or worse, but if successful it would add years to his life.
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Imp, my Trakehner gelding, had been a generous gift from a friend about five years ago. He was 19 then, and in addition to being a sweet and handsome guy, he was a talented and experienced upper-level dressage horse. He was also safe and sane under saddle, and his new job was to be my schoolmaster.

I moved Imp into a training barn, and all went well. He did have his quirks---he didn’t always get along with his pasturemates, he often demanded to be brought in well before his outside time was up, and he tended to have strong opinions about just about everything. But he was a dream to ride.

Then, just months later, Imp suddenly turned up head-bobbing lame. The veterinarian diagnosed a tear in his sesamoid ligament. Despite all our rehabilitative efforts, the injury would never heal enough for Imp to be brought back into even light riding. I brought him home to be a pasture horse, hoping that with enough time off, he might heal on his own. But one year stretched into several, and he never became fully sound. His strong personality simply became part of the atmosphere at the barn.

“What is wrong with his eye?” The question came from a friend who visited us in the fall of 2012. She had taken to Imp right away, loving his wavy long hair, regal bearing and quirky personality. But she’d also noticed a subtle change that, in my day-to-day care, I had missed.

I took a closer look. The inside corner of Imp’s left eye was angled downward, pulled by the skin around the eye. Thinking the skin had somehow adhered to the fascia0 below, I gently massaged the area, trying to get it to loosen.

When that didn’t help, I called my veterinarian, Katie Collier, DVM, of Fieldstone Veterinary Service in Grand Ledge, Michigan.

Wait and see

After a close examination that included x-rays, Collier confirmed that something was indeed very wrong. She explained that she saw a mass growing in the orbit (socket) behind Imp’s left eye and that it was pushing the eyeball outward, causing the skin around it to stretch.

We talked about treatment options, but none seemed reasonable or practical at that point. Trying to remove the mass would be very difficult without removing the eye, too, but Imp didn’t seem to be in any pain, so putting him through surgery that drastic didn’t seem right. We decided to just monitor the situation to see if the eye would get worse. Imp had worked hard during his life, and I was happy to focus on simply making his last years as pleasant as possible.

But as the months passed, Imp’s eye began bulging more noticeably. Michigan State University, with its large animal ophthalmology service, was only about a half hour away, and the worry that I hadn’t explored all the options nagged at me. So I made an appointment there in the spring of 2013.

Ophthalmology resident Freya Mowat, BVSc, PhD, examined Imp. She told me the mass behind his eye was most likely some type of cancer, and we discussed a variety of diagnostic options. None were appealing. A biopsy of the tumor would be difficult, given its location, and treatments to shrink it would likely have no significant impact.

Surgery to remove the mass would be painful and risky---and there was no guarantee that they could reach all of it or save the eye. If the tumor never got any worse, it might still be best to just let it be. But, I was told, if we left the tumor alone, it could also continue to grow in size until it began to affect Imp neurologically, or it could cause him so much pain his quality of life would be severely diminished.

With all of this information swirling in my head, I declined further diagnostics and made the decision to take Imp home without pursuing any treatments. The plan was to manage his pain as well as we could, with dexamethasone0 when necessary, until it might be time to consider humane euthanasia. I went home with literature on cancer and the services the hospital offered for making end-of-life decisions.

Imp seemed oblivious to his condition, and he remained just as demanding and charismatic as always. As the months passed, his eye was slowly pushed outward, while the skin around it stretched down. By fall, he started to become a bit more subdued, presumably from discomfort, but never to the point where it seemed to be his “time.”

A commitment to act

By winter it was clear Imp’s eye was getting worse. It had pushed out considerably, and there was some discharge from the eye and left nostril. But little else had changed. Imp was not deteriorating noticeably in any other way, and he wasn’t showing any neurological deficits from the growth of the tumor. I began to hope he might remain comfortable for a few more years.

Collier looked him over, and we discussed the possibility of removing Imp’s eye, but not the tumor, to alleviate any discomfort caused by the dislocation. That surgery should be simpler, we thought, and the stay at the MSU hospital would be short. I made an appointment for the late spring, when I would have time off from work to focus entirely on Imp and his recovery.

But suddenly the surgery wouldn’t wait. Imp’s condition worsened when the eye protruded so far that the third eyelid, also called the nictitating membrane, detached and was sometimes flipping outside the socket. I rescheduled the procedure for the earliest available appointment, in March 2014.

When we arrived, Mowat and her colleagues, including resident Ryan Boyd, DVM, examined Imp carefully. They noticed an ulcer on his eyeball, most likely a result of his inability to close his eyelids, that was causing him some pain. They also said it was time to remove his eye and, as Mowat explained to me, also the tumor below it.

The tumor, she suspected, was likely a rare type of cancer called an extra-adrenal paraganglioma (EAPG), which affects nerve cells. The good news was that these tumors tend to be slow-growing and don’t quickly spread to other parts of the body. On the other hand, EAPGs are very invasive locally. If Imp’s tumor ran out of room in the eye socket, it could spread in the other direction, eating through the bone of his skull toward his brain.

Mowat also said that surgery to remove the tumor would be difficult. EAPGs tend to be vascular and bleed extensively when disturbed. In fact, some horses bleed so profusely during the procedure that they need blood transfusions to save their lives. Mowat conferred with surgeon John Stick, DVM, DACVS, and they agreed that they could try to preemptively control any hemorrhage by ligation of the left carotid0 artery---closing the vessel off with a few dissolvable stitches before the tumor was removed. Even so, a donor horse would have to be on hand in case Imp needed a blood transfusion.

What I had hoped would be an easy, in-and-out procedure under local anesthesia had now become a complicated, risky surgery. If it worked, however, Imp might have many more happy, healthy years ahead of him.

I agreed it was worth a try.

Tricky surgery, rough recovery

I waited in a room adjacent to the surgical suite as Imp was prepped and placed under general anesthesia and the surgeons began their work. I wasn’t able to see what was going on, but I was OK with that.

After about two hours, someone from the surgical team came out to tell me the procedure was finished. Imp had lost substantially more blood than would be expected during a normal eye extraction, but not enough to require a transfusion. Mowat confessed later that it was unsettling for an ophthalmologist, who is not used to encountering so much blood in a procedure, to have to deal with such active bleeding. But the team’s plan worked well. By closing off the artery prior to removing the tumor, then packing the space tightly with gauze and covering it with a pressure bandage, they were able to stem the blood flow. As they’d suspected, they were not able to remove the entire tumor, but they were able to get enough that it would take years, maybe even decades, for the lesion to grow back to a problematic size.

I’d like to say Imp looked better when I saw him, but he really didn’t. His breathing was labored and he was sweating slightly. His vital signs---an elevated pulse and respiratory rate---indicated he was probably in pain due to the packing in his eye socket, Mowat explained, but it was necessary to control any bleeding that might persist.
He also had a heart murmur. It was unclear if the murmur had been there all along or was caused by the ligation of the carotid.

The sweating and labored breathing continued over the next couple of days, but even so, Imp was his usual charismatic self, digging into his bran mash with the energy of a horse half his age, playing with it and getting more on me than he did in his mouth.

Two days after the surgery, it was time to remove the gauze packing.
This could have disrupted the surgery site enough to cause Imp to bleed profusely again, but fortunately, the procedure was uneventful. The veterinary team filled the orbit with Gelfoam, a material that helps stop bleeding and can be left inside closed surgical wounds, and sewed the skin shut.

Removing the gauze reduced Imp’s pain, and his breathing returned to near-normal. His heart murmur also subsided to the point where, after five days in the hospital, he could go home.

Imp was happy to be back at the barn, but we would still encounter a few more bumps in his recovery. First, he started bleeding from the nose, which was expected, but not to this extent and not this long after the surgery. At a follow-up visit to MSU, however, an endoscopic exam of his nasal cavity showed nothing unusual, and the bleeding stopped a few days later.

After another week, the area around and under the stitches began looking abnormal to me. Collier came out to take a look. She thought the site looked fine and removed the stitches along with a lot of dead skin. Underneath, the site had been healing well.

Then a few days later, I discovered that the incision site had opened slightly and a large amount of gelatin-like pus had poured out onto Imp’s face. It appeared that, with the removal of the stitches, the incision site had weakened enough to allow an infection that had been trapped inside to work its way out.

After consulting with Collier, I applied a warm compress to the incision site several times a day to draw out the remaining infection, and we started another round of antibiotics. That combination seemed to resolve the problem, and from that point onward, Imp’s recovery went smoothly.

It is now six months after the surgery, and Imp is pretty much back to his normal self, minus one eye. He still demands to come in from his pasture on his schedule, pins his ears when being fed and talks to anyone who will listen. He suffers all the one-eyed-horse jokes cheerfully. But he does have one new habit: When he doesn’t want to do as I ask, he turns his head purposefully to the right. I guess he figures if he can’t see me, he can ignore me. I hope he has many more years to live comfortably and happily as my quirky, retired dressage horse.

This article was first published in EQUUS issue #450, March 2015. 

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